Probiotics Reduce Vibriosis in Farmed Shrimp

FRANCE - An industry linked research study by scientists at the French Research Institute for Exploitation of the Sea, has revealed positive benefits of using probiotics in shrimp production.

Studies evaluating the use of probiotics with farmed shrimp show positive production benefits.

The joint research program conducted by Mathieu Castex in Nouméa, New Caledonia (South Pacific), has demonstrated that the administration of Bactocell® (Pediococcus acidilactici MA 18/5 M) in the feed of marine shrimps (Litopenaeus stylirostris) in farms usually affected by summer syndrome, could reduce vibriosis-associated mortality by up to 15 per cent. As a result, final shrimp yield of the farm is increased.

The action of Bactocell in the shrimp were also evaluated and shown to be very positive. The probiotic improved digestive functions and the gut-associated bacteria populations of the shrimps.

Supported and Significant

The results of on-going Lallemand-IFREMER partnership on probiotic applications and its use in shrimp farming have been recently been published in peer-reviewed journal Aquaculture. These findings strengthen previous experimental and field data obtained with Bactocell in various shrimp species under different farming conditions. They show that this particular probiotic bacteria is an effective means of supporting sustainable shrimp farming.

Castex said that the present findings shed some light on the probiotic modes of action in shrimps.

"We looked at the effects Bactocell could have on the shrimps microbiology, digestive function and physiology, and how this could explain the benefits observed on the shrimps growth performance and resistance against vibriosis," he explained.

The research team first of all looked at the overall gut microbial content when the shrimps received Bactocell continuously with their diet. It appeared reduced, with particular reductions to the number of vibrios.

Vibriosis are one of the main causes of dramatic losses for major shrimp producing countries. In New Caledonia, where shrimp farming represents a substantial source of revenue, Litopenaeus stylirostris shrimp species is affected by two major vibriosis depending on the season, the summer and winter syndromes.

"There were also less vibrio pathogens in the shrimps heamolymph. This explains why, even though they were in the same ponds and submitted to the same pathogens pressure, that the shrimps which received Bactocell survived better to summer syndrome than those on the control diet," said Castex. Further work is being carried out at IFREMER to determine specific gut microbial populations.

Castex also notes that the study showed that Bactocell improved the shrimps nutrient storage process within their digestive gland. It also enhanced the activity of their digestive enzymes. "By improving the overall digestive process, Bactocell optimises feed utilisation, resulting in better feed conversion rates and growth performance. This is a property generally associated with probiotics in both aquatic and terrestrial animals, and it has been extensively demonstrated in the case of Bactocell in particular," he added.

Commercially Representative

The present study performed in conditions as close as possible to commercial farming was made possible thanks to an original experimental system designed by Dr Chim of IFREMER. This system uses floating cages in earthen ponds, allowing to grow "Control" and "Bactocell" -fed shrimps under identical conditions, minimising the impact of the environment on the outcome, a common issue when evaluating a feed additive effect in aquaculture commercial conditions.

Summer syndrome, caused by Vibrio nigripulchritudo first appeared in New Caledonia in 1997, and quickly became almost enzootic in the first shrimp farm affected.

Due to the significant economic impact, the local authorities and shrimp farmers association have now placed the research on vibriosis as a R&D priority for Caledonian aquaculture.

The Caledonia Aquaculture Department of IFREMER (the French Research Institute for Exploitation of the Sea) works in this area. The on-going research partnership with Lallemand is part of a global research program aimed at determining the causes and preventing vibriosis outbreaks in New Caledonia.